Process for making core spun yarns



- April 22, 1969 J. G. .SCRUGGS PROCESS FOR MAKING CORE SPUN YARNS FiledAug. 9, 1965 FIG.4.

INVENTOR. JACK e. SCRUGGS g TToRflEY United States Patent 3,439,491PROCESS FOR MAKING CORE SPUN YARNS Jack G. Scruggs, Cary, N.C., assignorto Monsanto Company, St. Louis, Mo., a corporation of Delaware FiledAug. 9, 1965, Ser. No. 478,217 Int. Cl. D02g 3/36, 3/38, 3/02 U.S. Cl.57-160 6 Claims ABSTRACT OF THE DISCLOSURE The present invention relatesto sheath-core yarns. More particularly, this invention relates tocomposite yarn structures comprised of core yarn having a sheath ofmicrofibers deposited thereon and a method for producing saidstructures.

Various methods have been developed in recent years to producemicrofiber yarns. Because of the unique properties exhibited by themicrofibers they have been found to be very useful for special purposes.The term microfibers as used herein refers to fibers having diameterswhich range from about 0.1 micron to about 15.0 microns with the averagediameter being between 2.0 and 5.0 microns. These fibers are generallyspun by feeding a synthetic organic polymer, in liquid state, to arotating surface where the polymer is discharged as elongated dropletsfrom the rotating surface by centrifugal force and the droplets becomeentrained in a stream of gas flowing parallel to the axis of therotating surface to form fibers which are transported to a collectionscreen. Regardless of the particular method used to prepare the fibers,the collection thereof employed has been similar in that the fibers aredeposited on a screen in the form of a web or batting. For textileprocesses such as knitting and weaving which employ yarn, the webs ofmicrofibers must be removed from the collection screens and roved intoyarn prior to being fashioned into fabrics. Because of the large rovingformed in this manner, extensive drafting is necessitated to provide thesmall denier yarns required for most fabricating operations.Furthermore, the low deniers that are preferred for some applicationscannot be easily prepared by the known processes.

Another disadvantage which has been experienced with the known methodsfor producing microfiber yarns is the high production cost of yarnscomposed entirely of microfibers. Also, these yarns are limited by thephysical properties and characteristics common to the material fromwhich the single component of microfibers are spun.

With the foregoing in mind, a primary object of the present invention isto provide composite yarns composed of a core yarn having a microfibersheath spun from a material other than the core yarn.

Another object of the invention is to provide composite yarns having acombination of unique properties.

Another object of the invention is to provide a method for depositing asheath of microfibers on a yarn to produce a composite yarn having thecombined characteristics and properties of the core yarn and the sheathfibers.

Another object of the invention is to provide a method for producing lowdenier yarns having the unique properties exhibited by microfiber yarns.

Another object of the invention is to provide an improved method ofproducing sheath-core yarns.

Another object of the invention is to provide a method for mechanicallyentwinging microfibers around a core yarn to produce a novel compositeyarn.

Other objects and advantages of the invention will be apparent from aconsideration of the description and claims which follow.

In general, the objects of this invention are accomplished by passing acore yarn essentially transversely through the fiber stream ofmicrofiber spinning operations such as described in copendingapplication Ser. No. 464,477 of T. E. Crompton filed June 16, 1965,whereupon the microfibers are deposited and mechanically entwined on thecore yarn in the form of parallel helixes to produce a compositestructure. Ssytems for preparing microfibers other than by cone spinningmay also be employed to carry out the present invention. The ratio inweight per unit length between the core yarn and the sheath fibers ispredetermined by the denier of the core yarn, the rate at which the coreis advanced through the fiber stream and the rate of microfiberformation. The spnning rate of the microfibers may be regulated withincertain limits to vary the sheath portion. Preferably, a false twist isimposed on the core yarn while passing through the path of themicrofibers to impart a wrapping action to the core which causes thesheath fibers to twist around the core and anchor thereon firmly toprovide the core with a uniform concentric sheath. Either a spindle typeor an air type false-twist device may be employed to cause the core yarnto rotate about its axis in the region of the microfiber stream. Iffalse twist is not imposed on the core yarn, a greater portion of themicrofibers tend to collect on one side thereof to form an eccentricsheath around the core. Whether false twist is employed or not, themicrofibers are securely entwined around the core yarn without the aidof an adhesive and remain compact throughout subsequent processes.

The materials satisfactory for the preparation of the composite yarn inaccordance with the present invention are comprised a wide selection.For example, material for the core yarn may include any of the organicpolymers and copolymers that can be solution or melt spun; materialssuch as metal, glass, ceramic, and inorganic compositions; naturalfibers such as cotton, wool, hemp, cellulose and bast fibers;elastomeric materials such as spandex or rubber, either natural orsynthetic; and any combination of the above materials which may beblended or spun as conjugates. The core may exist in the form of amonofilament, staple, continuous filament, ribbons of slit film, ortextured yarns, all of which may be fully drawn, partially drawn, orundrawn. Although a Wide range of materials may be utilized thepolyamides are preferred.

The sheath fibers may be compirsed of any of the so called airborne-typemicrodenier fibers. Such fibers are generated in a forced-fluid mediumand are generally called airborne fibers. While the polyacrylonitrilesand copolymers of acrylonitrile and other monomers copolymerizabletherewith are preferred, all other compositions of materials that can begenerated into fine denier fibers may be employed.

Prefrably, the core yarn and the sheath of microfibers are prepared fromdifferent materials so that the desirable qualities and advantages ofeach may be utilized. For example, the core yarn may be made from apolyamide to obtain strength and the sheath fibers made frompolyacrylonitrile which has a good hand, good ultraviolet lightstability, and good dyeing qualities. Thus, the two materials can becombined economically to produce a yarn which exhibits the goodqualities of both. Another example of an improved yarn prepared inaccordance with the present invention is a high bulk elastomeric yarnwhich is composed of an elastic core having a sheath of microfibersprepared from a selected material to provide certain desired properties.

A better understanding of the invention will be possible by reference tothe drawing in which:

FIGURE 1 is a diagrammatical arrangement of apparatus suitable forpracticing the invention;

FIGURE 2 is a section of the composite yarn, enlarged, to show thehelical arrangement of the sheath of microfibers;

FIGURE 3 illustrates a cross-sectional view, greatly magnified, of yarnproduced in accordance with the arrangement of apparatus shown in FIGURE1; and,

FIGURE 4 is a cross-section, greatly magnified, illustrating theeccentric core of yarn produced when false twist is not imparted to thecore yarn.

Referring specifically to FIGURE 1, there is shown a threadline or coreyarn being advanced essentially transversely through a stream ofmicrofibers 12. The microfibers may be prepared by any method capable ofproducing fibers suitable for the invention, but preferably a conespinning system 14, as shown, and being of the type disclosed in thecopending application Ser. No.

464,477 of T. E. Crompton filed June 16, 1965, is employed.

The core yarn 10 is withdrawn from a supply bobbin 16 by a pair of feedrolls 18 and advancing through an enclosure 20 wherein the microfibers.12 are collected on the moving threadline. As the threadline traversesthe path of the microfiber stream, more than 95 percent of them becomeentwined around the moving core to cover the surface thereof with amultiplicity of axially spaced helixes. A false twist is imparted to thecore yarn by a pneumatic false-twist device 22 to facilitate a moreuniform deposition of the microfibers on the core yarn and therebyproduce a c one-corespun yarn 24 having a concentrically located core asshown in FIGURE 3. The cone-corespun yarn 24 is then passed through awash bath 26 and taken up on a bobbin 28.

The threadline or core yarn 10 must be spaced far enough away from thecone 30 to permit the removal of solvent and tackiness from themicrofibers prior to their engagement with the core. If the solvent isnot removed from the microfibers, an undesirable sheet or mass ofmaterial is found on the core yarn. It has been found that for mostoperating conditions the distance may range from 1.0 to 5.0 feet, butdistances from 1.25 to 2.0 feet are preferred. Since the microfibers arediscontinuous and entrained in a gas stream moving at high velocity,they become firmly entwined around the threadline upon contact therewithto form an excellent mechanical bond.

As illustrated in FIGURE 1, the threadline 10 is directed slightly at anangle with the face of the cone. The oblique movement of the threadline10 with respect to the fiber stream 12 causes the microfibers to advanceaxially along and around the threadline to deposit the fibers thereon inthe shape of parallel helixes as shown in FIG- URE 2. It will beapparent however that the angle must be very small so that a properamount of wrapping or entwinement will occur to mechanically retain thesheath of imicrofibers in place on the core yarn.

An outstanding and unusual aspect of the present invention is displayedby the fact that almost 100 percent of the microfibers are collected onthe core yarn regardless of the denier. The sheath fibers arediscontinuous and may range in lengths from about 4; inch to severalinches. If the fibers are permitted to travel to a screen forcollection, they are deposited in a wide sheet. Quite unexpectedlyhowever, when a yarn having a denier which may range from about 15 toseveral hundred is drawn through the flow path of the microfibers, therelatively widely scattered fibers are attracted to the single smallthreadline. The core yarn may be of any size preferred, the onlyrequirement being that the strength thereof is suificient to withstandthe collecting process.

The relative proportions of the components combined to produce thecomposite yarn of this invention are practically unlimited. By varyingthe linear speed of the collecting threadline 10 and the rate ofmicrofiber output, a Wide range of core to sheath ratios can beobtained. For example, the core component could ultimately be totallyremoved by a selective eluting technique. This removal could beaccomplished either before or after the yarn has been formed into aproduct. Thus, all intermediate proportions between all core and nosheath or vice versa may be attained.

Composite yarns prepared in accordance with the present invention can bedrawn, twisted, plied, annealed, etc. within the usual limits forconventional yarns. These processing operations may be carried out usingconventional equipment.

The following examples illustrate specific embodiments of the invention.All parts and percentages are by weight unless otherwise specified. Testprocedures employed were as follows:

The abrasion resistance was determined as described in ASTM D11751.1.2;the air permeability was measured using the procedure described in ASTMD737; the water absorption was determined by placing 3 inch diameterdiscs of the woven fabrics in contact with a fritted glass funnelsurface. The surface of the disc not in contact with the funnel waspreviously attached, by the use of an adhesive tape having adhesive onboth sides and sold under the trademark Scotch brand tape, to a 3 inchdiameter cotton bag containing approximately 50 g. of fine lead shot.The applied weight held the fabric in intimate contact with the funnelsurface. The funnel contained water beneath the fritted glass surfaceand was directly connected to a meniscus which was calibrated to readdirectly weight of water, in grams absorbed. After allowing the sampleto come to equilibrium, the percent weight gain due to water absorbedwas calculated; and the insulation tests were carried out using anapparatus which consisted of two layers of 1 inch x 8 inches x 8 inchesMarinite, an insulating material containing asbestos fiber, diatomaceoussilica, and an inorganic binder, with a inch x 8 inches X 8 inchesaluminum plate sandwiched between the Marinite. The upper Marinite layercontained a square 4 inch hole to allow exposure of the fabric. Athermocouple was connected to the bottom of the aluminum plate. The testwas carried out by placing the fabric on top of the aluminum plate,fitting the top Marinite layer in place and exposing the sample toeither a 250 watt infrared heat lamp or a 150 watt lamp at a distance of6 inches. The temperature after 40 minutes exposure was selected forcomparing the insulating properties of the fabric.

EXAMPLE 1 A 19 percent solution of a copolymer of approximately 93percent acrylonitrile and 7 percent vinylacetate in dimethylacetamidewas pumped through the hollow drive shaft of a cone rotating atapproximately 4500 r.p.m. into an attenuating air stream in the mannertaught by T. E. Crompton in copending application Ser. No. 464,477 filedJune 16, 1965. Instead of collecting the fibers on a screen as describedin Ser. No. 464,477, the fibers were collected by passing a denier nylon66 yarn having a tenacity of 4.86 grams per denier and an elongation of36 percent through the path of the cone-formed microfibers. The nylonyarn was introduced and withdrawn at approximately f.p.m. at a distanceof approximately 2 feet from the rotating cone. The nylon core, nowcontaining a sheath of microfibers, was next passed through a pneumatictwister, such as described by E. P. Carter et al. in Ser. No. 466,159filed June 23, 1965, now US. Patent No. 3,303,639, set at 20 p.s.i.g.air pressure. The twisting device imparted false twist to the yarn whichproduced a wrapping action that wound the microfiber sheath around thenylon core. After the winding step, the composite yarn was then passedthrough a boiling water wash bath and taken up with a conventional takeup unit. The bobbin of washed yarn was dried in a vacuum oven and thendrawn 1.38 times over a hot shoe device at C. The

EXAMPLE 2 The procedure described in Example 1 was repeated with theexceptions that the drying step was omitted and the moist fiber drawnusing a steam drawing tube at a temperature of 126 C. The walls of thedrawing tube were electrically heated to 200 C. to prevent theaccumulation of condensate on the interior walls of the drawing tube.The composite yarn had essentially the same properties as the hot shoedrawn fiber in Example 1 with the exceptions that the modulus of theyarn was increased from 7.0 grams per denier to 15.0 grams per denier bysteam drawing, but the hot shoe drawn product was more lustrous inappearance than the steam tube drawn yarn.

EXAMPLE 3 The procedure described in Example 1 was repeated with theexceptions that a 204 denier, 34 filament, undrawn nylon 66 yarn wasused, the core drawn 1.5 time during the sheath collecting step, and thehot shoe draw ratio increased to 2.6 times. The yarn obtained had adenier of 154, a tenacity of 1.9 grams per denier and an elongation of19.6 percent. The composite yarn contained 65.0 percent acrylicmicrofiber.

EXAMPLE 4 The procedure followed in Example 1 was repeated with theexceptions that the undrawn nylon core used in Example 2 was drawn 2times prior to the microfiber collection step and was not drawn duringthe collection step. The final drawing of the composite fiber aftercollection of the microfiber sheath and drying was carried out on a hotshoe at a draw ratio of 2.4 times to give a product having a denier of164, a tenacity of 2.74 grams per denier, and an elonagtion of 20.7percent. The composite yarn contained 74.0 percent acrylic microfibersas a sheath.

EXAMPLE 5 The procedure followed in Example 1 was repeated with theexceptions that a 2-ply, 70 denier, 34 filament, textured nylon 66 coresold under the trademark Superloft Was employed for collecting theacrylic microfiber sheath and a draw ratio of 1.21 times was employed inthe hot shoe drawing. The bulky yarn obtained had a denier of 538, atenacity of 1.43 grams per denier, an elongation of 20.3 percent andcontained 79.5 percent microfiber sheath. The composite was converted toa very highly bulked condition by exposure to hot, humid conditions in arelaxed state.

EXAMPLE 6 The procedure described in Example 1 was repeated with theexceptions that a 350 denier spun cotton yarn having a tenacity of 1.8grams per denier and an elongation of 8.1 percent was employed as thecore yarn, and no drawing was carried out, either during the collectionstep or after washing and drying. The composite yarn had a denier of658, a tenacity of 1.4 grams per denier and an elongation of 11.8percent. The yarn contained 47.0 percent acrylic micrmofibers as aprotective sheath. When the fiber obtained in this example and theuncoated cotton yarn employed as the core were submitted to a gardensoil burial test for three months at room temperature the core sheathfiber properties were yarn was attacked by parasitic fungi and renderedunessentially unchanged while the unprotected cotton suitable forfurther use.

EXAMPLE 7 The procedure followed in Example 1 was repeated with theexception that a 420 denier spandex fiber core was used to collect themicrodenier acrylic fibers.

The core fiber was introduced at 54 f.p.m. and withdrawn at f.p.m. Thewashed fiber was drawn an additional 2.0 times in the steam tube deviceemployed in Example 2. The spandex core-acrylic micrmofiber sheath fiberhad a denier of 586, an elongation of 280 percent and a tenacity of 0.43gram per denier. 'Fabric made from these fibers had a soft, wool-likehand which was an improvement over the clammy feeling imparted tofabrics fashioned from uncoated spandex yarns.

EXAMPLE 8 The procedure described in Example 2 was repeated with theexception that a bicomponent, self-crimping fiber was employed as themicrofiber collecting core. The bicomponent fiber contained polyethyleneterephthalate as one component and a mixture of 90 percent polyethyleneterephthalate and 10 percent polycarbonate as the other component. Thebicomponent fiber containing an acrylic microfiber sheath was drawn 1.5times in a steam tube at 153 C. to give a bulky fiber with a woollikehand. The bulky nature of the fiber was further developed by exposure tosteam in a relaxed state.

EXAMPLE 9 The procedure described in Example 2 was repeated with theexceptions that a 308 denier-10 filament polypropylene core was employedto collect the microdenier fiber sheath, the twisting and washing stepswere omitted. The composite was simultaneously drawn 20 times andstripped of residual solvent in a steam tube at 194 C. The compositeyarn obtained had a denier of 487, a tenacity of 1.1 grams per denier,and elongation of 6.0 percent and contained 80 percent acrylicmicrofibers as a sheath.

EXAMPLE 10 The procedure followed in Example 1 was followed with theexception that drawing steps were omitted and the speed at which thecore yarn was introduced was varied to demonstrate a simple processavailable for controlling the core-sheath ratio. The commercial drawnnylon 66 core yarn and the core-sheath fibers were spun at speeds andhad properties shown in the following table.

TAB LE I Core speed Core-sheath Tenacity Elongation Acrylic (f.p.m.)yarn denier (gJdenier) (percent) microfiber (percent) EXAMPLE 11Composite yarn prepared as described in Example 1, was woven as fillinginto a crowfoot-weave fabric with 84 picks per inch using commercialnylon 66 as the warp yarn. An identical fabric sample was prepared withthe exception that a commercial acrylic, 3 denier per filament, totaldenier yarn was used as filling instead of the composite yarn obtainedin Example 1. The fabrics were tested for abrasion resistance, airpermeability, water absorption and insulation properties. The testresults are tabulated below in Table II.

TABLE II Abrasion Air perrne- Filling resistance ability (cu. WaterInsulation Test yarn (strokes to ftJmin. at absorption infrared whitefailure) 0.5 in. press (percent) 0.) 0.)

drop) Control.-- 76 199 130 74. 8 47. 5 From Ex. 1- 310 52 195 68.5 43.3

EXAMPLE 12 The procedure followed in Example 1 was employed with theexception that a 861 denier nylon 66 core containing a conventionalultraviolet stabilizer was passed through the microfiber stream at aspeed of 140 f.p.m. The resulting composite yarn was not drawn furtherand had a denier of 991, a tenacity of 7.16 grams per denier, anelongation of 20.2 percent and contained 13 percent microfibers as asheath. The microfiber sheath-containing yarn produced in this examplewas compared with a coreyarn without a sheath coating by exposing bothin a Fade- O-Meter for 60 standard Fade-O-Meter hours and then measuringthe percent loss in strength. The sheath containing yarn lost 251percent of its strength while the unprotected fiber lost 5.60 percent ofits strength. Therefore, a sheath protected yarn will retain about 70percent of its original strength after exposure to 100 standard Fade-O-Meter hours whereas the unprotected yarn will retain only about 30 to 40percent of its original strength.

From the data of the foregoing examples it is apparent that the yarnscontemplated by the present invention and products made therefrom haveseveral unique and useful properties. Heretofore, it has not beenpossible to so easily and economically combine the various fibers topromote the unusual properties of each and also compensate for thedeficiencies which exist in particular applications. One example of howthe outstanding properties of two materials are combined so that aweakness of each is overcome by the other will be recognized in the useof nylon cord covered with acrylic fibers for flood control purposes. Amaterial having the strength of nylon is re quired for sand bags butbecause of poor ultraviolet stability the bags are useful for only ashort duration. On the other hand acrylic fibers are not strong likenylon, but are quite stable for extended periods of outdoor usage.Consequently, when nylon cord is coated with acrylic fibers inaccordance with the present invention an excellent yarn is produced foruse in flood control projects which will Withstand adverse weatherconditions for extended periods. Other important advantages and productsresulting from the invention are properties such as increased bulk, goodhand, improved dyeability, flame retardance and fiber covered electricalconducting wires which may be woven into blankets, heating pads, carpetsand the like.

The foregoing detailed description has been given for clearness ofunderstanding only, and unnecessary limitations are not to be construedtherefrom. The invention is not to be limited to the exact details shownand described since obvious modifications will occur to those skilled inthe art.

What is claimed is:

1. A method of producing composite yarns composed of a core strand and asheath of fibers mechanically entwined around said strand, comprising:

(a) generating a multiplicity of fine denier fibers in a high velocitygaseous medium,

(b) directing the fibers toward a collecting zone by the gaseous medium,

(c) advancing a threadline through the collecting zone at an obliqueangle with the path of the fibers,

(d) depositing the fibers on the moving threadline,

(e) causing the threadline to rotate about its natural axis to wrap thefibers uniformly around said threadline and mechanically entwine saidfibers thereon to form a composite yarn, and

(f) collecting the composite yarn in an orderly manner.

2. A method of producing composite yarns composed of a core strand and asheath of microdenier fibers mechanicaly entwined around said strand toprovide the composite yarn with a uniform cover sheath having improvedultraviolet light stability, comprising:

(a) generating a multiplicity of microdenier fibers in a confined area,

(b) directing the fibers under the force of a gaseous medium along apredetermined path in the confined area,

15 (c) advancing a strand through said confined area generallytransversely across the path of said fibers,

(d) causing the strand to rotate about its natural axis whereupon thefibers wrap uniformly around the strand to form a concentric sheaththereon, and

00 (e) withdrawing the strand from said confined area.

3. A method for mechanically entwining microfibers around a continuousstrand, which comprises:

(a) advancing a fiber-forming material onto a rotating surface to form amultiplicity of microdenier fibers in a confined area,

(b) advancing a continuous threadline through the confined areaapproximately 1.0 to 5.0 feet from the rotating surface,

(c) entraining the microfibers in a stream of gas moving at a highvelocity sufficient to direct said fibers against said threadline withsuflicient force to tightly entwine the said fibers around saidthreadline to form a composite yarn, and

(d) collecting the composite yarn.

4. The method of claim 3 in which the threadline traverses the confinedarea at an oblique angle with the path of the fibers whereby helicalwrapping of the fibers is accomplished.

5. The method of claim 4 in which the threadline is caused to rotateabout its natural axis to increase the entwinement of said fibers.

6. The method of claim 5 in which the composite yarn is drawn at least1.5 times to improve yarn properties.

References Cited UNITED STATES PATENTS 1,990,337 2/1935 Lewis et al 575X 2,131,598 9/1938 Obermaier 57-5 2,208,897 7/1940 Dockerty et a1. 57-52,241,405 5/1941 Hyde et a1. 57-5 2,411,559 11/1946 Sonin et a1 117-332,902,820 9/1959 Bronson et a1. 57163 2,997,837 8/1961 Breen et al 571393,009,309 11/1961 Breen et a1. 57139 JOHN PETRAKES, Primary Examiner.

US. Cl. X.R.

